Humidifier for a horizontal flue



FIG. 1 is a front view with the back view being identical in appearance.

FIG. 2 is a top view;

FIG. 3 is a bottom view; and,

FIG. 4 is a side view with the opposite side view being identical in appearance. 

The ornamental design for a humidifier for a horizontal flue, as shown and described. 